Q1 of 113 Page 560

Prove that

sin(1500 + x) + sin (1500 – x) = cos x


In this question the following formula will be used:


Sin( A +B)= sinA cos B + cosA sinB


Sin( A - B)= sinA cos B - cosA sinB


= sin150 cosx + cos 150 sinx + sin150 cosx – cos150 sinx


=2sin150cosx


=2sin(90 + 60)cosx


=2cos60cosx


=2cosx


=cosx


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